Tank for electrolytic processing



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0% f? N Nb Hg April 19, 1960 c. H. PARspNs TANK FOR ELECTROLYTIC PROCESSING 5 Sheets-Sheet 2 Filed March 18 1953 QQH NNW FL MN @NH i own Nwwl N mmw gm mow QQ X 5 Sheets-Sheet 3 IHI C. H. PARSONS TANK FOR ELECTROLYTIC PROCESSING April 19, 1960 Filed March 1a, 1955 April 19, 1960 c. H. PARSONS 2, 3

' TANK FOR ELECTROLYTIC PROCESSING Fi led March 18, 1953 5 Sheets-Sheet 4 I jagaum nite States iPatent O TANK FOR ELECTROLYTIC PROCESSING Curtis H. Parsons, Prospect Heights, 11]., assignor to Fansteel Metallurgical Corporation, a corporation of New York Application March 18, 1953, Serial No. 343,045

Claims. (Cl. 204-199) This invention relates to a tank for electrolytic processing, and is particularly adapted for simultaneous treatment of a large number of small articles. While the invention is of general application, it is particularly useful in the formation of an oxide film on tantalum electrodes for use in condensers, rectifiers and the like.

In the formation of films by anodic oxidation-an operation designated as formingon such film forming metals as tantalum, aluminum, or the like, it is of utmost importance that uniformity of the product be maintained. The formation of a film on such a metal is affected by such factors as temperature and concentration of the electrolyte. The characteristics of the film formed on the metal, such as tantalum, used as the anode in a condenser, determine the magnitude of the potential that can be blocked, as well as the capacitance per unit area of the electrode.

In the design of equipment for forming electrodes, the electrochemical characteristics of the various parts of the tank or apparatus for forming the electrodes become important. While it is possible to fabricate parts of materials which are electrically nonconducting and chemically inert to an electrolyte, such as glass or other similar materials, it is of course necessary to establish metallic electrical connections to the Work pieces to be formed. It is impractical to insulate electrically a large number of connections to such work pieces by conventional means.

Hence, the design of a tank mechanism for forming a large number of electrodes is complicated by the necessity for eliminating all current paths except the desired current path between a cathode through the electrolyte and the work pieces as anodes. When direct current is used in such an electrode-forming tank, any soluble metallic anode which is not protected from corrosion will dissolve into the electrolyte, and the metal constituting the anode may be deposited on the cathode.

In accordance with this invention, I provide a tank construction wherein the parts may be fabricated of metal, and wherein such metal parts are completely protected against corrosion and electrolytic action. By virtue of such protection, the usual advantages of strength, ease of manufacture of various parts, ruggedness to mechanical shock, lightness, and electrical conductivity when required, are all obtained.

In the description of the invention, a particular application of the invention to the requirements of formation of tantalum anodes is disclosed. Insuch a tank, the electrolyte is customarily alkaline in nature and is maintained at an elevated temperature. For that reason, the various portions of the structure are preferably made of tantalum or tantalum-clad metals when exposed to the electrolyte, and other portions are made of'a plastic material, such as polytetrafluoroethylene, available in the trade under the name of Teflon. It has been found that this material is stable and resists the action of chemicals under -the conditions necessary for. the formation of tantalum electrodes.

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However, it is to be understood that the tank forming the subject matter of the present invention may be used for other purposes, or may have tantalum anodes formed therein in electrolytes other than alkaline so that, where conditions warrant, materials other than tantalum or Teflon may be used. Even in the case of the formation of tantalum anodes with an alkaline electrolyte, other mate-' rials besides Teflon may be used where such other materials have desired mechanical and chemical properties.

In order that the invention may be understood, an

exemplary embodiment thereof will be described, it being understood, however, that various modifications in the".

mechanical structure, as well as in the nature of the 'various materials, may be made without departingfrom the broader aspects of the invention.

Referring now to the drawings: Figure 1 is a sectional elevation'of a tank embodyin the present invention, this figure showing a fragmentary detail of an electric motor for driving the rotary magazine assembly;

Figure2 is a section along line 2-2 of Figure 1; Figure 3 is a fragmentary perspective detail of a corner of one electrode;

Figure 4 is-a plan view of the tank illustrated in Figure 1, Figure 4, however, omitting the fragmentary view of the electric motor;

Figure 5 is a sectional detail along line 5-.-5 of Fig ure 4;

Figure 6 is a view, partly in section, of the rotary magazine assembly removed from the tank;

Figure 7 is a detail of a part of a magazine;

Figure 8 is a sectional detail along line 8-8 of Fig-v ure 6;

Figure 9 is a detail looking down along line 9-9, of

Figure 16 is a sectional detail of the heater, assembly I and mountingfor the tank;

Figure 17 is a sectional detail along line 17--17 of Figure 16. I

The construction includes suitable motive means 10 (Fig. 1), shown as part of an electric motor, but which in practice may include variable speed means for providing any desired speed of rotation of shaft 11. Shaft 11 drives coupling 12 having any suitable construction and being of electrically insulating material. 12 has sleeve 14 supporting the end of composite shaft generally indicated by 15. Shaft 15 is shown in detail in Figure 13. This shaft includes central core 16 of electrically conducting material, such as copper, brass,

or even steel. For tantalum forming, it is preferred to have core 16 of tantalum. Since the shaft core will have a substantial cross sectional area compared to any Disposed around core 16 is shaft sleeve 17 of electri cally insulating material which is chemically inert to theelectrolyte under operating conditions, for example" Other materials, such as glass, rubber. (natural or synthetic), nylon, or other insulating materials having patented Apr. 19, 1960- Coupling suitable characteristicsmay be used. The core and sleeve are snugly fitted to prevent creepage'of electrolyte.

Composite shaft 15 has slip ring 20 of brass or other suitable metal around the outside of sleeve 17 in proximity to coupling sleeve 14. Slip ring 20 is electrically connected to shaft core 16 by tapered pin 21 extending transversely of the composite shaft. Brush 22 (Fig. l) rideson the slip ring to provide a sliding electrical contact therewith.

. The composite shaft extends through stufiing box 24. This consists of cylindrical member 25 having bore 26 (Fig. 13). Cylindrical member 25 has one end 27 threaded and has its other end 28 enlarged to form an annular flange. Inwardly of flanged end 28 is cylindrical portion 30 having its inner portion 31 externally threaded.

Disposedwithin bore 26 of cylindrical member 25 is metallic sleeve 33 having ends 34 and 35 turned respectively inwardly and outwardly to form flanges. Sleeve 33 is preferably of tantalum-and the endflanges may be obtained by spinning. Bushing 37 of inert insulating material, such as Teflon, is fitted within sleeve-33 at flanged end 35. Within sleeve 33 and adjacent bushing 37 is coil spring 38 of steel or other suitable metal. A glass spring may be used if desired. Washer 39 fits between sleeve'33' and the outer surface of shaft 17, and takes the thrust of coil spring 38. p

-A stack of washers 40 of Teflon or other inert mate rial follows washer 39. Stack 40 has end washers 41 and 42, which are flat on their outer sides-and provided with annular V concave and convexportions respectively on their inner sides. The remaining washers in the stack have their sidescorrespondingly shaped, one side of each washer'having an annular V projection and the othe'r side having an annular V depression. The configuration and number of the washers may be varied to suit required conditions.

Bushing 44, preferably of inert material, such as Teflon, lies within sleeve 33 adjacent flange 34 and takes the endthrust of the washer stack. Threaded over-end portion 27 of cylindrical member 25 is nut 45 of suitable material. Nut 45 may be of metal, such as stainless steel. Nut 45 is cup-shaped and clears shaft portion 17.

Adjacent to nut 45 is washer 46 preferably of'inert material such as Teflon. This washer fits snugly over shaft portion 17 and presses against theouter face of nut 45; The outer face of nut 45 is machined or finished smooth so that friction between nut 45 and washer 46 is low. Nut 45 is drawn up tightly, as is usual in stufiing boxes.

The entire stuffing box is rigidly secured in wall 48 of a. tank to be described. Flat washer 49 of metal is disposed against the shoulder formed by flange28. Retainer ring 50 having a cuppedshape is disposed'against the outer end surface of flanged portion 28. ring 50 is welded or otherwise rigidly attached to flat washer 49. Retainer ring 58 has inner edge portion 51 overlying inwardly directed flange 34. Washer 49 and retainer ring 50 are preferably of tantalum. Side wall.

48 of the tank is suitably apertured, with the wall edge disposed opposite shoulder 30. The stufiing box. is rigidly bolted to the tank side by threaded collar 53. The collar is preferably of metal, such as stainless steel,

Retainer and engages threaded portion 31 of cylindrical memgroove therebetween. Tantalum sheet 60'is attachedyto the opposed faces of parts 58 and 59' and also over the .pipe 70 preferably carries cold water.

4 face of partition 57. Sheet 60 (Fig. 13) is rigidly attached to shaft core 16 by suitable means, such as bolt 61. Coupling member 55 is fixedly attached to shaft 15 by transverse tapered pin 62.

Referring now to the tank itself (Figures 1 and 4), the tank, generally indicated by 65, has one end wall 48, previously referred to, and opposite end wall 66. Rounded tank body 67 extends between the tank ends. The entire tank may be constructed of suitable material. Thus, glass-lined metal, or metal sheet consisting of one or more layers, may be used. The tank may be of tantalum-clad steel or nickel, the tantalum being on the inside. It is understood that the tank ends and body are joined as by welding to provide tight seams.

Cover 68 may be of any suitable material, either metallic or nonmetallic. The cover may conveniently be of glass. Attached to the inside of the cover face is coiled pipe 70 which may also be of glass. Pipe 70 may carry hot water to maintain an elevated cover temperature, or may carry cold water for condensing vapors. In the particular tank described for forming tantalum electrodes, The electrolyte is maintained at an elevated temperature. Condensation of vapor at the cover prevents loss of vapor and permits condensed vapor to return to the main body of the electrolyte. Thus, electrolyte concentration will be maintained apart from possible loss inherent in the formation process. Flexible hose 71 and 72 may be used to couple pipe 70 to a water system. Other liquids than water may be used if desired. Cover 68 may rest on tank 65 and be readily removable therefrom.

While the tank may be externally heated, there is'provideda bayonettype heater 74 along the tank bottom. The heater details are illustrated in in Figures 16 and 17. The heater illustrated here uses steam; however, an electric heater may be used. The significant construction details relate'to the mounting of the heater on the tank wall. As illustrated here, the heater has inner metal tube 75 of any suitable material. Tube 75 has open end 76 and lateral slots 77. Tube 75 lies within outer tube 78 having sealed end 79. The outside of tube 78 is of material which is chemically inert under operating conditions. Tubef78- may be of tantalum, or tantalum-clad stainless steel with the tantalum on the outside. Spacer rings 80 are carried by inner tube 75 and maintain the free end of tube 75 in fixed relation to outer tube 78.

Inner tube 75 has portion 81 extending outside of tank 65 and may be connected to a steam supply by suitable means; Portion 81 of the inner tube passes through T fitting 82 having threaded parts 83, 84 and 85. Part 83 has packing nut 86 for providing a seal around pipe portion 81 and supporting the same. Part is connected to apipe or drain for spent steam or condensate. Part 84'has nipple 87 threaded into it. Nipple 87 is threaded into disk 88 of stainless steel or other suitable metal. Disk 88 has countersunk apertures for accommodating electrically insulating bushing 90. These bushings are shouldered, and may be of Teflon or other chemically inert material. The number ofapertures may vary, there being four here. Bolts 91 extend through the bushing apertures and engage threaded openings in metal collar 92. Collar 92 has its inner surface threadedand is disposed over bushing 94. Bushing 94 has a flange 95. Bushing 94 may be of stainless steel and has a sheath oftantalum thereover. Thus, flange 95 is covered by ring 96 and washer-.97 in a manner similar to stufiing box 24. The inside surface of bushing 94 has metal sleeve 98 provided with flange. 99. Metal sleeve 98 also is preferably of tantalum. Between sleeve 98 and tube 78 is insulating sleeve v offTeflon or other inert material. Adjacent flange 99 is insulating washer 101, also of'Teflon orother insulating material. Washer 101 extends down to outer tube 78. Metal washer 102 is disposed against washer 101. Washer 102 has flange 103' overlying the end of tube 78;

Tank end wall 66 has a suitably apertured part for accommodating the heater assembly. The tank wall is clamped between collar 92 and flange 94. Bolts 91 are drawn up tightly enough to provide a seal.

Suspended within tank 65 is sheet electrode 105 (Fig. 2), which is corrugated for increasing the electrode area. Electrode 105 is also perforated to promote flow of electrolyte. Electrode 105 is of metal, such as tantalum, and has bent clips which hang from metal rods 106 and 107. These rods are also of tantalum and are supported in insulating bushings 108 (Fig. l) at the tank ends. Bushings 108 are press fitted in suitable apertures in the tank walls. Electric conductors 109 are attached to one or more of the rod ends.

Rotatively supported within tank 65 is a magazine assembly. This assembly, shown in Figure 6, has hollow metal shaft 111 of tantalum. Pressed into the ends of shaft 111 are insulating rods 112 and 113. The insulating rods are retained in position by pins 114 and 115.

Insulating rod 112 has cylindrical head 117. Insulating washer 118 is provided between the inside face of head 117 and the edge of shaft 111. Head 117 functions as a shaft and is rotatively supported on block 120 (Fig. 1). This block is of insulating material and has a semi-cylindrical bearing surface. The block is rigidly supported on tank wall 66 by bolts 121 passing through the tank wall.

Insulating rod 113 (Fig. 6) has cylindrical head portion 123 ('Fig. 1), also supported on block 124 of insulating material. Block 124 is provided with a semicylindrical bearing surface to support head portion 123. Block 124 is cut away at 125 to clear ring 51 of the stufiing box assembly. Block 124 is supported from tank wall 48 by bolts 126. The various insulating parts are of Teflon or other suitable material.

Head portion 123 (Fig. 14) has tongue 128 for fitting into the groove formed by parts 58 and 59 of female coupling member 55 (Fig.' Tongue 128 is covered by sheet metal 129 for establishing a detachable electrical connection with metal 60 of the female coupling member. Metal 129 is attached to tongue 128 by suitable means, such as rivets, and is electrically connected to metal rod 130 disposed axially within head 123 and rod 113 (Fig. 6). The connection may be established by pin 131 passing through sheets 129 and rod 130. Pin 115 provides an electrical connection between rod 130 and shaft 111. The recess for rod 130 preferably does not extend the full length of insulating rod 113 in order to minimize leakage of liquid. The entire assembly carried by hollow shaft 111 may be raised from the tank when tongue 128 lies in a vertical plane.

Hollow shaft 111 c'arriesat its ends metal disks 135 and 136. These two disks are rigidly secured to shaft 111 as by welding. The outer edges of disks 135 and 136 are bent toward each other to form annular flanges 137 and 138. 'Each disk carries a series of bolts 140 disposed at intervals around the disk edge, the two disks having bolt pairs aligned axially of shaft 111. Each bolt 140 has offset portion 141 welded to the disk and has straight portion 142 passing through an aperture in the disk flange. Bolt portion .142 extends radially out from the disk and is threaded. Each bolt 140 has nut Supported between each pair of axially aligned bolts 140are pairs of magazines 145. Each pair of magazines consists of two parts 146 and 147 longitudinally aligned. 'Each magazine part has a generally H-shaped and 151. The center and side strips are welded or riveted to form an H beam. Sides 150 and 151 have their edges bent to form clip support flanges 152 to 155 inclusive. The center strip 149 of each magazine part extends at 156 beyond sides 150 and 151 at the outer ends only. Reinforcing strip 156a is provided at extension 156. The

6 reinforced extension has a lateral cut-out at 157 adapted to accommodate bolt part 142.

The adjacent inner ends 159 of each magazine part are rigidly attached to reinforcing member 160. Each member 160 consists of strip 161 (Fig. 11) doubled over on itself and having flanges 162 formed on opposite sides. The aligned magazine portions and reinforcing member are joined to form a two-part magazine. The two parts may be detachably secured to each other.

The inside end of each reinforcing member has rigidly attached thereto clip 165 having jaws 166 and 167. The aligned clip jaws engage the edge of intermediate support member 170 (Fig. 6). This support member may consist of a metal disk or, as shown in Figure 5, two semicircular disk parts bolted together at 171 and rigidly attached to hollow shaft 111. Intermediate support memher 170 may have two layers of metal for stifiening.

Carried by each of flanges 152 and 155 (Fig. 10) inclusive are clips 173. Each clip has a right angle mounting portion 174 for rigid attachment to a flange and side portion of a magazine. Each clip also has contact-making portion 175, suitably apertured at 175a, and provided with opposed spring jaws 176. Jaws 176 have sharp cutting edges and are bent toward each other. Any work piece, such as electrode 178, to be treated can be inserted through aperture 175a and tightly gripped by jaws 176. The jaws will cut through any coating or layer present on work piece 178 to make intimate electrical contact. At

the same time, a work piece is mechanically retained in position during treatment.

An entire magazine may be removed from'the rotary assembly by loosening nuts 143 (Fig. 6) and pulling the magazine at the center to disengage jaws 166 and 167 from support member 170.

In order to treat work pieces, the. magazines are loaded. A source of direct current is connected to brush 22 (Fig. 1) and one or more wires 109. Shaft 111 is rotated at desired speed by motor 10. A suitable electrolyte is disposed in the tank, and the heater and condensing coils are put into operation.

The work circuit is between electrode 105 (Fig. 2) through the electrolyte to work pieces 178 (Fig. 7), then through the magazine body and associated structure to shaft 111 (Fig. 6), then through rod 13!), metal pieces 60 and 129 in coupling members 123 and 55, core 16 and then to brush 22.

The tank, shaft 111 and accessories, like the heater for example, may have chemically inert, electrically insulating surfaces, such as glass. The magazine, and particularly the work piece engaging clips, are ofmetal.- In order to prevent electrolytic action on metal surfaces forming part of the structure, as distinguished from any work pieces, and also to confine the flow of electricity to work piece surfaces, it is preferred to form a blocking layer'on such structural surfaces. Where tantalum work pieces are to be treated electrolytically in the tank construction above disclosed, it is preferred to use tantalum for all metal whose surface is contacted by the electrolyte. The clips 173 (Fig. 6), magazine 145, disk members 135, 136 and 170, and shaft 111 are therefore preferably made of oxide-filmed tantalum. The current flowing through the work pieces supported by the magazines must, therefore, traverse the oxide coatings thereon in flowing from one of these elements to another on its way between wire 109 and brush 22. The important thing, however, is that mostof the current (by current is meant the movement of electrons or negative ions) which flows through the electrolyte in the tank should first pass through the section having central strip 149 (Fig. 10) and sides 150 work pieces rather than the surrounding metal surfaces. The workpieces, being initially unfilmed and made of a conductive material, offer much less resistance to the flow of current than the surrounding filmed surfaces, and hence will initially receive the major share of the current flowin in the electrolyte. 1

Other film-forming metals, such as aluminum for ex-- ample, may be used, provided the film is stable under operating conditions. Such metals as aluminum and tantalum, when formed with oxide blocking-layer films, have their films maintained when immersed in a suitable electrolyte and connected to a source of positive potential. Electrolytes which are used to form oxide films on tantalum work pieces, such as tantalum anodes for use in electrolytic rectifiers and condensers, will of course be suitable to maintain the oxide film on the metal surfaces of the tank, which are also made of tantalum. The blocking layers or films on the structural surfaces of the magazine and associated elements of the tank construction of the present invention are formed to withstand potentials higher than any potential which may be used in processing work pieces so that the blocking layer film thereon will not be destroyed. Inasmuch as the formation of blocking layers on various metals is well known, no further description of such formation will be given.

The polarity of current passing between brush 22 and wire 199 is such that the blocking layer on all structural metal surfaces will provide an insulating surface. Brush 22 is made positive relative to wire 109 in order that the work pieces may be connected as anodes and the magazine and associated metallic surfaces will have their oxide films maintained. As a result, work pieces 178 will form electrodes of one polarity and electrode 165 will form an electrode of opposing polarity.

In the case of tantalum forming, electrode 105 will be a cathode for current conduction. All other metal parts in the tank which are electrically connected to each other will function as anodes. The blocking layer on such anodes will suffice to prevent current fiow. Work pieces 173 of tantalum may be formed into anodes for use in con densers, rectifie-rs and the like. The cutting grip applied to a suitable part of the work piece will establish good contact between the work piece and its holding clip. The rotation of the magazine assembly in the tank will insure uniform electrolyte conditions for all work pieces.

The general tank construction disclosed here may be used in various electrolytic processes where work pieces are anodes. Thus, anodizing of various metals, such aluminum for example, may be carried out. The filmed metal parts in electrical contact with the anode and electrolyte will be protected against corrosion. With tantalum structural parts treated to withstand potentials of about 200 volts, such filmed parts will withstand substantially all electrolytic processes, which usually require lower potentials.

What is claimed is:

1. An electro-forming tank comprising a receptacle having a tantalum interior surface, a cathode suspended in said receptacle, a rotary assembly in said receptacle, said assembly including a tantalum shaft, shaft extensions of insulating material secured to the ends of said tantalum shaft, bearings of insulating material Within said receptacle for engaging said insulating shaft extensions so that said tantalum assembly is insulatingly supported from said receptacle, an insulating shaft having a tantalum core passing from said receptacle to the outside, insulating means for supporting said insulating shaft on said receptacle so that said shaft is insulatingly supported while being susceptible to being driven by external motor means, means for mechanically connecting said insulating shaft with said tantalum shaft for driving the same, means for electrically connecting the;metal core of said insulating shaft to said tantalum shaft, tantalum clips having sharp jaws connected to said tantalum shaft for gripping work pieces and cutting through any electrical insulating film on the work pieces, means for establishing an electrical connection externally of the tank to the core of said insulating shaft, said work pieces held by said clips being at least as great as that used across the cathode and anode Work piece.

2. A tank for use in electrochemical operations, said tank comprising a receptacle having an open top, means at the bottom of said receptacle for heating an electrolyte in said receptacle, a removable cover for said receptacle, said cover having cooling means for condensing vapor upon the inside thereof, insulating blocks secured to said receptacle at the inside thereof, said blocks having semicylindrical recesses for supporting a shaft, a stufiing box supported on the outside of said receptacle, said stufiing box being aligned with said two bearing blocks and the receptacle wall being apertured to permit a shaft to pass through from said bearing blocks into said stufi'ing box, a composite shaft having an outer portion of insulating material and a core of metal, said composite shaft passing through said stuffing box into the interior of said receptacle, said composite shaft terminating in a shaftcoupling element, a second shaft rotatably supported on said bearing blocks within said receptacle, said second shaft having a member cooperating with said coupling element and being detachable therefrom for rotatively coupling said composite shaft and second shaft together, said second shaft having insulating ends resting upon said bearing blocks but having a metal portion extending between said insulating ends and normally lying in electrolyte, said detachable coupling elements having metal contacting members for providing metallic contact between the metallic portion of said second shaft and the inner core of said composite shaft, metal flange members carried by the metallic portion of the second shaft, metal magazine members supported between said metal flange members, each magazine member having means for supporting at least one work piece thereon, said supporting means having a cutting edge for establishing good electrical contact with said work piece, all of the metal forming the magazine, flanges and shaft portions that are accessible to electrolyte being made of film forming metal having a film formed thereon capable of withstanding any potential to be impressed across the electrodes in said tank, means for connecting the metal core of said compositeshaft in an electrical circuit and an electrode suspended in said electrolyte connected to the other pole of said electrical circuit, said electrode being connected as a cathode and the filmed metal functioning as anodes blocking the flow of current from said anode parts into said electrolyte whereby said work pieces are the only anode elements carrying substantial current.

3. The construction according to claim 2, wherein the film forming metal is tantalum and the insulating material is polytetrafluoroethylene.

4. The consruction according to claim 2, wherein the means for supporting work pieces include spring jaws of tantalum, said jaws having cutting edges for establishing metallic contact with a work piece.

5. The construction according to claim 2., wherein each magazine member comprises an elongated member having a generally H-shaped section, and wherein a plurality of metal clips are disposed along the edges of said elongated member for holding work pieces.

References Cited in the file of this patent UNITED STATES PATENTS 888,067 Daniels May 17, 1908 "1,154,604 Boissier Sept. 28, 1915 1,906,378 7 Howard May 2, 1933 2,346,386 Nankewis Apr. 11, 1944 2,390,282 7 Tour et al. Dec. 4, 1945 2,432,322 Lundstrom Dec. 9, 1947 2,572,838 Cohn Oct. 30, 1951 OTHER REFERENCES Yelton: Transactions of the Electromechanical Society, vol. 90, (1946), pp. 331 to 339.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2 933 443 April 19 1960 Curtis H, Parsons It is hereby; certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4 line 34, strike out in" second occurrence; column 6, line 18, for "152 and 155" read 152 to 155 column 7 line 41 after "such" insert as column 8 line 52 for "construction" read construction Signed and sealed this 20th day of September 1960,

(SEAL) Attest:

KARL H. AXLINE Attesting Officer ROBERT C. WATSON Commissioner of Patents 

1. AN ELECTRO-FORMING TANK COMPRISING A RECEPTACLE HAVING A TANTALUM INTERIOR SURFACE, A CATHODE SUSPENDED IN SAID RECEPTACLE, A ROTARY ASSEMBLY IN SAID RECEPTACLE, SAID ASSEMBLY INCLUDING A TANTALUM SHAFT, SHAFT EXTENSIONS OF INSULATING MATERIAL SECURED TO THE ENDS OF SAID TANTALUM SHAFT, BEARINGS OF INSULATING MATERIAL WITHIN SAID RECEPTACLE FOR ENGAGING SAID INSULATING SHAFT EXTENSIONS SO THAT SAID TANTALUM ASSEMBLY IS INSULATINGLY SUPPORTED FROM SAID RECEPTACLE, AN INSULATING SHAFT HAVING A TANTALUM CORE PASSING FROM SAID RECEPTACLE TO THE OUTSIDE, INSULATING MEANS FOR SUPPORTING SAID INSULATING SHAFT ON SAID RECEPTACLE SO THAT SAID SHAFT IS INSULATINGLY SUPPORTED WHILE BEING SUSCEPTIBLE TO BEING DRIVING BY EXTERNAL MOTOR MEANS, MEANS FOR MECHANICALLY CONNECTING SAID ISULATING SHAFT WITH SAID TANTALUM SHAFT FOR DRIVING THE SAME, MEANS FOR ELECTRICALLY CONNECTING THE METAL CORE OF SAID INSULATING SHAFT TO SAID TANTALUM SHAFT, TANTALUM CLIPS HAVING SHARP JAWS CONNECTED TO SAID TANTALUM SHAFT FOR GRIPPING WORK PIECES AND CUTTING THROUGH ANY ELECTRICAL INSULATING FILM ON THE WORK PIECES, MEANS FOR ESTABLISHING AN ELECTRICAL CONNECTION EXTERNALLY OF THE TANK TO THE CORE OF SAID INSULATING SHAFT, SAID WORK PIECES HELD BY SAID CLIPS BEING METALLICALLY CONNECTED TO SAID CONNECTION-ESTABLISHING MEANS SO THAT SAID WORK PIECES FUNCTION AS ANODES, SAID VARIOUS TANTALUM SURFACES WITHIN SAID RECEPTACLE HAVING A FILM FORMED THEREON CAPABLE OF WITHSTANDING A POTENTIAL AT LEAST AS GREAT AS THAT USED ACROSS THE CATHODE AND ANODE WORK PIECE. 